Conventionally, the present applicant has already proposed a control apparatus for an internal combustion engine, as disclosed in in PTL 1. The engine is provided with a variable intake cam phase mechanism of a hydraulically-driven type. The variable intake cam phase mechanism changes an intake cam phase, which is a phase of an intake cam for opening and closing an intake valve, with respect to a crankshaft, between a predetermined most advanced value and a predetermined most retarded value. In this case, when the intake cam phase is controlled to the predetermined most advanced value, a valve overlap period becomes maximum.
In the case of the above variable intake cam phase mechanism, since it is the hydraulically-driven type, there is a fear that when foreign matter, such as sludge, is mixed in a hydraulic pressure circuit, a malfunction of a hydraulic pressure control valve or the like occurs. In the control apparatus, as described hereinafter, cleaning control of the variable intake cam phase mechanism (hereinafter referred to as the “intake-side cleaning control”) is performed during a decelerating fuel-cut operation (hereinafter referred to as the “decelerating FC operation”). First, the intake cam phase is controlled to a most retarded value at a time when the decelerating FC operation is started, and the intake cam phase is controlled to a most advanced value at a time when a predetermined time period has elapsed after the start time of the decelerating FC operation.
Then, at a time when an execution time period over which the control of the intake cam phase to the most advanced value has been performed reaches a predetermined value, it is determined whether or not the intake cam phase has reached the most advanced value, and the variable intake cam phase mechanism is controlled such that the intake cam phase is changed from the most advanced value to the most retarded value. By the above cleaning control, it is possible to prevent foreign matter, such as sludge, from causing a malfunction of the hydraulic pressure control valve or the like.
Further, it is described in PTL 1 that in a case where a variable exhaust cam phase mechanism capable of changing an exhaust cam phase is provided in the engine, cleaning control of the variable exhaust cam phase mechanism (hereinafter referred to as the “exhaust-side cleaning control”) may be performed.